Method of the preparation of an insulated aluminum alloy magnet wire

ABSTRACT

AN INSULATED SOLID MAGNET WIRE, PREPARED FROM AN ALUMINUM ALLOY WIRE HAVING AN ACCETABLE ELECTRICAL CONDUCTIVITY OF AT LEAST SIXTY-ONE PERCENT (61%) BASED ONE THE INTERNATIONAL ANNEALED COPPER STANDARD AND A MINIMUM OF FIFTEEN PERCENT (15%) ULTIMATE ELONGATION, HAS IMPROVED PHYSICAL PROPERTIES OF INCREASED TENSILE STRENGTH AND FATIGUE RESISTANCE WHEN COMPARED TO CONVENTIONAL MAGNET WIRE. THE ALUMINUM ALLOY WIRE CONTAINS SUBSTANTIALLY EVENLY DISTRIBUTED IRON ALUMINATE INCLUSIONS IN A CONCENTRATION PRODUCED BY THE ADDITION OF MORE THAN ABOUT 0.30 WEIGHT PERCENT IRON AND NO MORE THAN 0.15 WEIGHT PERCENT SILICON TO AN ALLOY MASS CONTAINING LESS THAN ABOUT 99.70 WEIGHT PERCENT ALUMINUM AND TRACE QUANTITIES OF CONVENTIONAL IMPURITIES NORMALLY FOUND WITHIN A COMMERICAL ALUMINUM ALLOY. THE SUBSTANTIALLY EVENLY DISTRIBUTED IRON ALUMINATE INCLUSIONS ARE OBTAINED BY CONTINUOUSLY CASTING AN ALLOY CONSISTING ESSENTIALLY OF LESS THAN ABOUT 99.70 WEIGHT PERCENT ALUMINUM, MORE THAN 0.30 WEIGHT PERCENT IRON, NO MORE THAN 0.15 WEIGHT PERCENT SILICON AND TRACE QUANTITIES OF TYPICAL IMPURITIES TO FORM A CONTINUOUS ALUMINUM ALLOY BAR, HOT-WORKING THE BAR SUBSTANTIALLY IMMEDIATELY AFTER CASTING IN SUBSTANTIALLY THAT CONDITION IN WHICH THE BAR IS CAST TO FORM CONTINUOUS ROD WHICH IS SUBSEQUENTLY DRAWN INTO WIRE WITHOUT INTERMEDIATE ANNEALS AND ANNEALED AFTER THE FINAL DRAW. AFTER ANNEALING, THE WIRE HAS THE AFOREMENTIONED NOVEL AND UNEXPECTED PROPERTIES OF A MINIMUM OF FIFTEEN PERCENT (15%) ULTIMATE ELONGATION, ELECTRICAL CONDUCTIVITY OF AT LEAST SIXTY-ONE PERCENT (61%) OF THE INERNATIONAL ANNEALED COPPER STANDARD AND INCREASED TENSILE STRENGTH, BENDABLITITY AND FATIGUE RESISTANCE.

United States Patent 6 Int. Cl. C22f N04 US. Cl. 148-2 Claims ABSTRACTOF THE DISCLOSURE An insulated solid magnet wire, prepared from analuminum alloy wire having an acceptable electrical conductivity of atleast sixty-one percent (61%) based on the International Annealed CopperStandard and a minimum of fifteen percent ultimate elongation, hasimproved physical properties of increased tensile strength and fatigueresistance when compared to conventional magnet wire. The aluminum alloywire contains substantially evenly distributed iron aluminate inclusionsin a concentration produced by the addition of more than about 0.30weight percent iron and no more than 0.15 weight percent silicon to analloy mass containing less than about 99.70 weight percent aluminum andtrace quantities of conventional impurities normally found within acommercial aluminum alloy. The substantially evenly distributed ironaluminate inclusions are obtained by continuously casting an alloyconsisting essentially of less than about 99.70 weight percent aluminum,more than 0.30 weight percent iron, no more than 0.15 weight percentsilicon and trace quantities of typical impurities to form a continuousaluminum alloy bar, hot-working the bar substantially immediately aftercasting in substantially that condition in which the bar is cast to formcontinuous rod which is subsequently drawn into wire withoutintermediate anneals and annealed after the final draw. After annealing,the wire has the aforementioned novel and unexpected properties of aminimum of fifteen percent (15%) ultimate elongation, electricalconductivity of at least sixty-one percent (61%) of the InternationalAnnealed Copper Standard and increased tensile strength, bendability andfatigue resistance.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a divisionof Ser. No. 814,201, filed Apr. 7, 1969, now Pat. No. 3,513,252 which isin turn a continuation-in-part of my copending application Ser. No.795,038, filed Jan. 29, 1969 which is in turn a continuation-in-part ofmy copending application, Ser. No. 779,376, filed Nov. 27, 1968, whichis in turn a continuation-in-part of my copending application Ser. No.730,933, filed May 21, 1968, all now abandoned.

DISCLOSURE This invention relates to an insulated solid magnet wire andmore particularly concerns an insulated magnet wire prepared from a wirehaving an acceptable electrical conductivity and improved tensilestrength and bendability at a standard minimum ultimate elongation.

The use of various aluminum alloy wires (conventionally referred to asEC wire) as wire windings for electromagnets is well established in theart. Such alloys characteristically have conductivities of at leastsixty-one ice percent (61%) of the International Annealed CopperStandard (hereinafter sometimes referred to as iAOS) and chemicalconstituents consisting of a substantial amount of pure aluminum andsmall amounts of conventional impurities such as silicon, vanadium,iron, copper, manganese, magnesium, zinc, boron and titanium.

Prior art aluminum alloy wire (EC wire) has proven acceptable in magnetwire applications only when low values for tensile strength areadequate. It has been found that conventional EC wire must be annealedto a dead soft condition (tensile strength of about 9,000 to 11,700psi.) before the ultimate elongation thereof increases to fifteenpercent (15 or above (an industry accepted minimum for magnet wire).When processing wire with a tensile strength as low as 9,000 to 11,700p.s.i., great care must be taken to avoid undue breakage and undesireddrawing of the wire. In fact, EC aluminum has generally provenunacceptable for use as magnet wire because of its low tensile strengthat an acceptable percent elongation.

When a prior art EC aluminum wire, having the required conductivity, arelatively high tensile strength and a relatively low ultimateelongation, is subjected to repeated and quite often sharp bendingduring a magnet winding operation, it typically breaks or developssurface fractures due to fatigue at the point of bending. Similarly, useof a prior art EC aluminum wire having the required conductivity, arelatively low tensile strength, and a relatively high ultimateelongation in the previously mentioned manner has yielded unsatisfactoryresults because the required pulling forces frequently encountered tendto break the wire. Furthermore, it is quite difficult to manufacture anEC wire of relatively low tensile strength because the pulling forcesapplied during processing of the wire cause breakage of the wire orundesirable stretching and reduction of the wire.

Thus, it becomes apparent that a need has arisen within the industry foran insulated aluminum magnet wire which has both relatively high tensilestrength and acceptably high ultimate elongation, and also possesses anability to withstand numerous bends at one point and to resist fatiguingduring processing of the wire. Therefore, it is an object of the presentinvention to provide an insulated aluminum magnet wire of acceptableconductivity and improved physical properties such that the wire may beused as an electro-magnet winding. These and other objects, features andadvantages of the present invention will become apparent to thoseskilled in the art from a consideration of the following detaileddescription of the invention.

In accordance with this invention, the present insulated solid magnetWire is prepared from an alloy containing less than about 99.70 weightpercent aluminum, more than about 0.30 weight percent iron, and no morethan 0.15 Weight percent silicon. Preferably, the aluminum content ofthe present alloy comprises about 98.95 to less than about 99.45 weightpercent with particularly superior results being achieved when fromabout 99.15 to about 99.40 weight percent aluminum is employed.Preferably, the iron content of the present alloy comprises about 0.45weight percent to about 0.95 weight percent with particularly superiorresults being achieved when from about 0.50 weight percent to about 0.80weight percent iron is employed. Preferably, the silicon content doesnot exceed 0.07 weight percent. The ratio between the percentage ironand percentage silicon must be 1.99:1 or greater. Preferably, the ratiobetween percentage iron and percentage silicon is 8:1 or greater. Thus,if the present aluminum alloy contains an amount of iron within the lowarea of the present range for iron content, the percentage of aluminummust be increased rather than increasing the percentage of siliconoutside the ratio limitation previously specified. It has been foundthat a properly processed insulated magnet wire, having aluminum alloyconstituents which fall within the abovespecified ranges, possessesincreased tensile strength at an acceptable ultimate elongation,acceptable conductivity and improved fatigue resistance.

The present solid aluminum alloy magnet wire is prepared by initiallymelting and alloying aluminum with the necessary amounts of iron orother constituents to provide the requisite alloy for processing.Normally, the content of silicon is maintained as low as possiblewithout adding additional amounts to the melt. Typical impurities ortrace elements are also present within the melt, but only in tracequantities such as less than 0.05 weight percent each with a totalcontent of trace impurities gen erally not exceeding 0.15 weightpercent. Of course, when adjusting the amounts of trace elements, dueconsideration must be given to the conductivity of the final alloy sincesome trace elements affect conductivity more severely than others. Thetypical trace elements include vanadium, copper, manganese, magnesium,zinc, boron and titanium. If the content of titanium is relatively high(but still quite low compared to the aluminum, iron and siliconcontent), small amounts of boron may be added to tie-up the excesstitanium and keep it from reducing the conductivity of the wire. Iron isthe major constituent added to the melt to produce the alloy of thepresent invention. Normally, about 0.50 weight percent iron is added tothe typical aluminum component used to prepare the present alloy, Ofcourse, the scope of the present invention includes the addition of moreor less iron together with the adjustment of the content of all alloyingconstituents.

After alloying, the melted aluminum composition is continuously castinto a continouus bar. The bar is then hot-worked in substantially thatcondition in which it is received from the casting machine. A typicalhot-working operation comprises rolling the bar in a rolling millsubstantially immediately after being cast into a bar.

One example of a continuous casting and rolling operation, capable ofproducing continuous rod as specified in this application, is asfollows.

A continuous casting machine serves as a means for solidifying themolten aluminum alloy metal to provide a cast bar that is conveyed insubstantially the condition in which it solidified from the cotninuouscasting machine to the rolling mill which serves as a means forhotforming the cast bar into rod or another hot-formed product in amanner which impartsv substantial movement to the cast bar along aplurality of angularly disposed axes.

The continuous casting machine is of conventional casting wheel typehaving a casting wheel with a casting groove partially closed by anendless belt supported by the castnig wheel and an idler pulley. Thecasting Wheel and the endless belt cooperate to provide a mold into oneend of which molten metal is poured to solidify and from the other endof which the cast bar is emitted in substantially that condition inwhich it solidified.

The rolling mill is of conventional type having a plurality of rollstands arranged to hot-form the cast bar by a series of deformations.The continuous casting machine and the rolling mill are positionedrelative to each other so that the cast bar enters the rolling millsubstantially immediately after solidification and in substantially thatcondition in which it solidified. In this condition, the cast bar is ata hot-forming temperature within the range of temperatures forhot-forming the cast bar at the initiation of hot-forming withoutheating beween the casting machine and the rolling mill. In the eventthat it is desired to closely control the hot-forming temperature of thecast bar within the conventional range of hot-forming temperatures,means for adjusting the temperature of the cast bar may be placedbetween the continuous casting machine and the rolling mill with- 4 outdeparting from the inventive concept disclosed herein.

The roll stands each include a plurality of rolls which engage the castbar. The rolls of each roll stand may be two or more in number andarranged diametrically opposite from one another or arranged at equallyspaced positions about the axis of movement of the cast bar through therolling mill. The rolls of each roll stand of the rolling mill arerotated at a predetermined speed by a power means such as one or moreelectric motors and the casting wheel is rotated at a speed generallydetermined by its operating characteristics. The rolling mill serves tohot-form the cast bar into a rod of a crosssectional area substantiallyless than that of the cast bar as it enters the rolling mill.

The peripheral surfaces of the rolls of adjacent roll stands in therolling mill change in configuration; that 15, the cast bar is engagedby the rolls of successive roll stands with surfaces of varyingconfiguration, and from different directions. This varying surfaceengagement of the cast bar in the roll stands functions to knead orshape the metal in the cast bar in such a manner that it is worked ateach roll stand and also to simultaneously reduce and change thecross-sectional area of the cast bar into that of the rod.

As each roll stand engages the cast bar, it is desirable that the castbar be received with sufficient volume per unit of time at the rollstand for the cast bar to generally fill the space defined by the rollsof the roll stand so that the rolls will be efiective to work the metalin the cast bar. However, it is also desirable that the space defined bythe rolls of each roll stand not be overfilled so that the cast bar willnot be forced into the gaps between the rolls. Thus, it is desirablethat the rod be fed toward each roll stand at a volume per unit of timewhich is sufficient to fill, but not overfill, the space defined by therolls of the roll stand.

As the cast bar is received from the continuous casting machine, itusually has one large flat surface corresponding to the surface of theendless band and inwardly tapered side surfaces corresponding to theshape of the groove in the casting wheel. As the cast bar is compressedby the rolls of the roll stands, the cast bar is deformed so that itgenerally takes the cross-sectional shape defined by the adjacentperipheries of the rolls of each roll stand.

Thus it will be understood that with this apparatus cast aluminum alloyrod of an infinite number of different lengths is prepared bysimultaneous casting of the molten aluminum alloy and hot-forming orrolling the cast aluminum bar.

The continuous rod produced by the casting and rolling operation is thenprocessed in a reduction operation designed to produce continuous wireof various gauges between eight (8) gauge AWG (cross-sectional diameteror greatest perpendicular distance between parallel faces of 0.128 inch)and forty (40) gauge AWG (cross-sectional diameter or greatestperpendicular distance between parallel faces'of 0.0031). The unannealedrod (i.e., as rolled to f temper) is cold-drawn through a series ofprogressively constricted dies, without intermediate anneals, to form acontinuous wire of desired diameter. If a cross-sectional shape otherthan round is desired, the drawn wire may be worked to a proper shape bycold-rolling or further drawing through appropriately shaped rollers ordies to produce the shaped wire. Typical cross-sectional shapes otherthan round are square and rectangular. At the conclusion of this drawingand optional shaping operation, the alloy wire will have an excessivelyhigh tensile strength and an unacceptably low ultimate elongation, plusa conductivity below that which is industry accepted as the minimum foran electrical conductor, i.e., sixty-one percent (61%) of IACS. The wireis then annealed or partially annealed to obtain a desired tensilestrength and cooled. At the conclusion of the annealing operation, it isfound that the annealed alloy wire has properties of acceptable minimumpercent elongation together with unexpectedly improved tensile strengthand percent conductivity and surprisingly increased bendability andfatigue resistance as specified in this application. The annealingoperation may be continuous as in resistance annealing, inductionannealing, convection annealing by continuous furnaces, or radiationannealing by continuous furnaces; or may be batch annealed in a batchfurnace. In addition, the present aluminum alloy wire may be partiallyannealed by resistance or induction annealing and then additionallyannealed by batch annealing. In a preferred embodiment of the invention,the present wire is in-line annealed by gas convection and/or radiationannealing. When continuously annealing, temperatures of about 450 F. toabout 1200 F. may be employed with anealing times of about five minutesto about of a minute. Generally, however continuous annealingtemperatures and times may be adjusted to meet the requirements of theparticular overall processing operation so long as the desired tensilestrength is achieved. In a batch annealing operation, a temperature ofapproximately 400 F. to about 750 F. is employed with residence times ofabout twenty-four (24) hours to about thirty (30) minutes. As mentionedwith respect to continuous annealing, in batch annealing the times andtemperatures may be varied to suit the overall process so long as thedesired tensile strength is obtained. Simply by Way of example, it hasbeen found that the following tensile strengths in the present aluminumalloy magnet wire are achieved with the listed batch annealingtemperatures and times.

During the continuous casting of this alloy, a substantial portion ofthe iron present in the alloy precipitates out of solution as ironaluminate intermetallic compound (FeAl Thus, after casting the barcontains a dispersion of FeAl in a supersaturated solid solution matrix.The supersaturated matrix may contain as much as 0.17 weight percentiron. As the bar is rolled in a hotworking operation immediately aftercasting, the FeAl particles are broken-up and dispersed throughout thematrix inhibiting large cell formation. When the rod is then drawn toits final gauge size without intermediate anneals and then aged in afinal annealing operation, the tensile strength, elongation andbendability are increased due to the small cell size and additionalpinning of dislocations by preferential precipitation of FeAl on thedislocation sites. Therefore, new dislocation sources must be activatedunder the applied stress of the drawing operation and this causes boththe strength and the elongation to be further improved.

The properties of the present aluminum alloy wire are significantlyaffected by the size of the FeAl particles in the matrix. Coarseprecipitates reduce the percent elongation and bendability of the wireby enhancing nucleation, and, thus, formation of large cells which, inturn, lowers the recrystallization temperature of the wire. Fineprecipitates improve the percent elongation and bendability by reducingnucleation and increasing the recrystallization temperature. Grosslycoarse precipitates of FeAl cause the wire to become brittle andgenerally unusable. Coarse precipitates have a particle size of above2,000 angstrom units and fine precipitates have a particle size of below2,000 angstrom units.

Following the annealing operation, the aluminum alloy electricalconductor is continuously insulated in a standard magnet wire continuousinsulating operation. A typical insulating operation comprises passingthe solid conductor through a bath of enamel. As the conductor passesthrough the bath, a continuous insulating enamel coat is applied aroundthe conductor. The coated conductor is then baked in a continuousfurnace. The insulating enamel should be one which is capable ofinsulating the solid conductor and the enamel should be of a thicknesssufficient to insulate the solid conductor and withstand the physicalhazards associated with winding of magnet wire. The preferred insulatingmaterial is an enamel such as the oleoresinous type, but other coatingssuch as fabrics, polyethylene, polypropylene, poly (vinyl chloride),polyurethanes, epoxies, a polyvinyl formal resin, a polyvinyl formalresin and an overcoat of nylon, a urethane modified polyvinyl formalresin, an acrylic resin, a polyurethane base and a nylon overcoat, amodified polyester base with a linear polyester overcoat, a polyimideresin, cotton yarn and polyester-s may also be employed. Typically,thermoplastic materials are applied by means of an extrusion head whichcoats the conductor with the thermoplastic material as the conductormoves through the head.

A typical No. 12 AWG solid insulated magnet wire of the presentinvention is prepared from a solid wire which has physical properties of15,000 p.s.i. tensile strength, ultimate elongation of twenty-fivepercent (25%), conductivity of sixty-one percent (61%) IACS, andbendability of thirty (30) bends to break. Ranges of physical propertiesgenerally provided by a suitable No. 12 AWG wire prepared from thepresent alloy include tensile strengths of about 12,000 to about 17,000p.s.i., ultimate elongations of about forty percent (40% to aboutfifteen percent (15% conductivities of about sixty-one percent (61%) toabout sixty-three percent (63%), and number of bends to break of aboutforty-five (45) to about fifteen (15). Preferred wires suitable for usein the present invention have a tensile strength of between 13,000 and15,000 p.s.i. an ultimate elongation of between thirtyfive percent (35%)and twenty-five percent (25%), a conductivity of between sixty-onepercent (61%) and sixty-three percent (63%) and number of bends to breakof between thirty-five (35) and twenty (20).

A more complete understanding of the invention will be obtained from thefollowing examples.

EXAMPLE NO. 1

A comparison between prior uninsulated EC aluminum magnet wire and theuninsulated wire of the present aluminum magnet wire is provided bypreparing an 15C alloy with aluminum content of 99.73 weight percent,iron content of 0.18 weight percent, silicon content of 0.059 weightpercent, and trace amounts of typical impurities. The present alloy isprepared with aluminum content of 99.45 weight percent, iron content of0.34 weight percent, silicon content of 0.056 weight percent and traceamounts of typical impurities. Both alloys are continuously cast intocontinuous bars and hot-rolled into continuous rod in similar fashion.The alloys are then cold-drawn through successively constricted dies toyield #12 AWG continuous round wire. Sections of the wire are collectedon separate bobbins and batch furnace-annealed at various temperaturesand for various lengths of time to yield sections of the prior EC alloyand the present alloy of varying tensile strengths. Several samples ofeach section are tested in a device designed to measure the number ofbends required to break each sample at a particular flexure point.Through uniform force and tension, the device fatigues each samplethrough an arc of approximately The wire is bent across a pair of spacedopposed mandrels having a diameter equal to that of the uninsulatedwire. The mandrels are spaced apart a distance of of about 1 /2 timesthe diameter of the uninsulated wire. One bend is recorded after thewire is deflected from a vertical disposition to one extreme of the arc,returned back to vertical, deflected to the opposite extreme of the arc,and returned back to the original vertical disposition. The speed ofdeflection, force and tension are substantially equal for all testedsamples. The results are as follows:

TABLE IIA EC magnet wire Present magnet wire Several samples of the #12AWG uninsulated round magnet wire and EC alloy #12 AWG uninsulated roundmagnet wire, processed as previously specified, are then tested forpercent ultimate elongation by standard testing procedures. At theinstant of breakage, the increase in length of the wire is measured. Thepercent ultimate elongation is then figured by dividing the initiallength of the wire sample into the increase in length of the wiresample. The tensile strength of the wire sample is recorded as thepounds per square inch of crosssectional diameter required to break thewire during the percent ultimate elongation test. The results are asfollows:

TABLE IIB EC alloy wire Present alloy wire Percent Percent Tensileultimate Tensile ultimate strength elongation strength elongationEXAMPLES 2 THROUGH 7 Six aluminum alloys are prepared with varyingamounts of major constituents. The alloys are reported in the followingtable.

TABLE 111 Percent Percent Percent Example N0. Al Fe Si 8 cedurespecified in Example No. 1 is used for determining average number ofbends to break. The results are reported in the following table.

TABLE IV Percent Average No. Tensile ultimate of bonds strengthelongation to break From a review of these results it may be seen thatExample No. 2 falls outside the scope of the present invention inpercentage of components. In addition, it will be noted for Example No.2 that the percentage of ultimate elongation is somewhat lower thandesirable and the average number of bends to break the sample is lowerthan the remaining examples.

EXAMPLE NO. 8

iAn aluminum alloy is prepared with an aluminum content of 99.42 weightpercent, iron content of 0.50 weight percent, silicon content of 0:055weight percent and trace amounts of typical impurities. The alloy iscast into a continuous bar which is hot-rolled to yield a continuousrod. The rod is then cold-drawn through successively constricted dies toyield 12 AWG round wire. The Wire is collected on a 30 inch bobbin untilthe collected wire weighs approximately 250 pounds. The bobbin is thenplaced in a cold General Electric Bell Furnace and the temperaturetherein is raised to 480 F. The temperature of the furnace is held at480 F. for 3 hours after which the heat is terminated and the furnacecools to 400 F. The annealed wire is then passed through an enamelingbath and insulated with enamel, Under testing it is found that theinsulated alloy magnet wire has a conductivity of 61.6% IACS, a tensilestrength of 16,700 p.s.i. and a percentage ultimate elongation of 19.8%.

[EXAMPLE NO. 9

Example No. 8 is repeated except the Bell Furnace temperature is raisedto 500 F. and held for 3 hours prior to cooling. The annealed andinsulated alloy wire has a conductivity of 61.4% IAOS, a tensilestrength of 14,200 p.s.i. and a percentage ultimate elongation of 27%.

iEXAMPLE NO. 10

Example No. '8 is repeated except the Bell Furnace temperature is raisedto 600 F. and held 3 hours prior to cooling. The annealed and insulatedalloy wire has a conductivity of 61.2% IACS, a tensile strength of14,000 p.s.i. and a percentage elongation of 30%.

EXAMPLE NO, 11

Example No. 8 is repeated except the Bell 'Furnace temperature is raisedto 600 F. and held 1 /2 hours prior to cooling. The annealed andinsulated conductor has a conductivity of 61.5% LACS, a tensile strengthof 16,200 p.s.i. and a percentage elongation of 22.5%.

EXAMPIJE NO. =12

The alloy of Example No. 8 is cast into a continuous bar which ishot-rolled to yield a continuous f temper rod of diameter. The rod isthen cold-drawn through successively constricted dies to yield #14 AWGround 'wire. The wire is then redrawn on a Synchro Model BG--1=6 wiredrawing machine which includes a Synchro Resistoneal continuous in lineannealer. The wire is drawn to #28 AWG at a finishing speed of 3,300feet per minute and the in-line annealer is operated at 52 volts with atransformer tap setting at No. 8. The wire is then collected on a bobbinand batch furnace annealed as in Example No. 8 at a temperature of 500F. and a time of 1% hours. The annealed wire is then insulated byextruding a coat of polyester resin around the wire. The sample istested and it is found that the annealed wire has a conductivity of 62%IACS, a tensile strength of 15,550 p.s.i. and a percentage ultimateelongation of 24.5%.

EXAMPLE NO. 13

The alloy of Example No. 8 is cast into a continuous bar which ishot-rolled to yield a continuous temper rod of diameter. The rod is thencold-drawn on a Synchro Style No. F X 13 wire drawing machine whichincludes a continuous in line annealer. The rod is drawn to #12 AWGround magnet wire at a finishing speed of 2,000 feet per minute and thein line annealer voltage at preheater #1 is 35 volts, at preheater #2 is35 volts, and at the annealer is 22 volts. The three transformer tapsare set at #5. The annealed wire is continuously insulated by beingpassed through an extrusion head where a coat of oleoresinous typeenamel is applied. The sample is tested and it is found that theannealed wire has a conductivity of 62% IACS, a tensile strength of ll6,400 p.s.i. and a percentage ultimate elongation of 20%.

One of the more interesting aspects of the present magnet wire alloy isthat during the annealing operation the percentage elongation increasesat a higher tensile strength than when annealing EC magnet wire alloy.In addition, when annealing EC magnet wire alloy, one must take the wirealloy almost to a dead soft condition before the percentage elongationbegins to improve. With the present alloy the percentage elongationimproves more steadily as annealing times and temperatures are increasedand it is possible to achieve an acceptable percentage elongation wellbefore attaining a dead soft condition in the wire.

It should be understood that the present invention con cerns insulatedmagnet wire and processes for its preparation. Magnet wire may assumemany cross-sectional configurations and while the present disclosure hasbeen primarily concerned with round magnet wire, the present inventionalso includes square and rectangular magnet wire.

'While this invention has been described in detail with particularreference to preferred embodiments thereof, it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention as described hereinbefore and as defined in theappended claims.

I claim:

1. Process for preparing an insulated magnet wire having an electricalconductivity of at least sixty-one percent IACS, a percentage elongationof at least 15%, a tensile strength of at least 12,000 p.s.i. and ironaluminate inclusions with a particle size of less than 2000 angstromunits, comprising the steps of:

(a) alloying from about 98.95 to about 99.45 weight percent aluminum,from about 0.45 to about 0.95 weight percent iron, about 0.01 to about0.15 weight percent silicon, and less than 0.05 weight percent each oftrace elements selected from the group consisting of vanadium, copper,manganese, magnesium, Zinc, boron and titanium; the total weight percentof trace elements being no more than 0.15 weight percent and the ratioof iron to silicon being at least 8:1;

(b) casting the alloy into a continuous bar in a moving mold formed by agroove in the periphery of a casting wheel and an endless belt lyingadjacent the groove along a portion of the periphery of the wheel;

() hot-working the bar substantially immediately after casting while thebar is in substantially that condition as cast by rolling the bar inclosed roll passes to obtain a continuous aluminum alloy rod;

(d) drawing the rod with no intermediate anneals to form wire;

(e) annealing or partially annealing the wire; and

(f) coating the annealed wire with an insulating mate rial.

2. Process of claim 1 wherein step (a) comprises alloying from about98.95 to about 99.44 weight percent aluminum, about 0.55 to about 0.95weight percent iron, from about 0.01 to about 0.15 weight percentsilicon, and less than 0.05 weight percent each of trace elementsselected from the group consisting of vanadium, copper, manganese,magnesium, zinc, boron and titanium.

3. Process of claim 1 wherein the individual trace element content isfrom 0.0001 to 0.05 weight percent and the total trace element contentis from 0.004 to 0.15 weight percent.

4. Process of claim 1 wherein step (e) comprises batch annealing orbatch partially annealing the Wire.

5. Process of claim 1 wherein an enamel is employed as the insulationmaterial.

6. Process for preparing an insulated magnet wire having an electricalconductivity of at least sixty-one percent IACS, a percentage elongationof at least 15%, and a tensile strength of at least 12,000 p.s.i.,comprising the steps of:

(a) alloying from about 98.95 to about 99.45 weight percent aluminumwith about 0.45 to about 0.95 weight percent iron, about 0.01 to about0.15 weight percent silicon, and from 0.0001 to 0.05 weight percent eachof trace elements selected from the group consisting of vanadium,copper, manganese, magnesium, zinc, boron and titanium, the total traceelement content being from 0.004 to 0.15 weight percent.

(b) continuously casting the alloy into a continuous bar;

(0) continuously rolling the bar in substantially that condition inwhich it was cast into a bar to form a continuous rod;

((1) drawing the rod with no intermediate anneals to form wire;

(e) annealing or partially annealing the wire; and

(f) coating the annealed wire with an insulating material.

7. Process of claim 6 wherein step (a) comprises alloying from about98.95 to about 99.44 weight-percent aluminum, about 0.55 to about 0.95weight percent iron, from about 0.01 to about 0.15 weight percentsilicon, and from 0.0001 to 0.05 weight percent each of trace elew mentsselected from the group consisting of vanadium, copper, manganese,magnesium, zinc, boron and titanium, the total trace element contentbeing from 0.004 to 0.15 weight percent.

8. Process of claim 6 wherein the insulating material is an enamel.

9. Process for preparing an insulated magnet wire having an electricalconductivity of at least sixty-one percent IACS, a percentage elongationof at least 15 a tensile strength of at least 12,000 p.s.i. and ironaluminate inclusions with a particle size of less than 2000 angstromunits, comprising the steps of:

(a) alloying from about 98.95 to about 99.45 weight percent aluminum,from about 0.45 to about 0.95 weight percent iron, about 0.01 to about0.15 weight percent silicon, and less than 0.05 weight percent each oftrace elements selected from the group consisting of vanadium, copper,manganese, magnesium, zinc, boron and titanium; the total weight percentof trace elements being no more than 0.15 weight percent and the ratioof iron to silicon being at least 8:1;

(b) casting the alloy into a bar;

(c) hot-working the bar by rolling the bar in closed roll passes toobtain an aluminum alloy rod;

(d) drawing the rod with no intermediate anneals to form wire;

(e) annealing or partially annealing the wire; and

(f coating the annealed wire with an insulating material.

10. Process for preparing an insulated magnet wire having an electricalconductivity of at least sixty-one percent IACS, a percentage elongationof at least 15%, and a tensile strength of at least 12,000 p.s.i.,comprising the steps of:

(a) alloying from about 98.95 to less than 99.44 weight percent aluminumwith about 0.55 to about 0.95 weight percent iron, about 0.01 to about0.15 weight percent silicon, and from 0.0001 to 0.05 weight percent eachof trace elements selected from the group consisting of vanadium,copper, manganese, magnesium, zinc, boron and titanium, the total traceelement content being from 0.004 to 0.15 weight percent;

(b) casting the alloy into a bar;

(c) hot-rolling the bar to form a continuous rod;

(d) drawing the rod with no intermediate anneals to form wire;

(e) annealing or partially annealing the wire; and

(f) coating the annealed wire with an insulating material.

References Cited UNITED STATES PATENTS 3,571,910 3/19'71 Bylund 29-52772,252,421 8/1941 Stroup 75-138 2,545,866 3/1951 'Whitzel et al. 291933,063,832 11/1962 Snyder 75-138 3,241,953 3/1966 Pryor et al 75-1383,278,300 /1966 Kloke 75-138 3,397,044 8/ 1968 Bylund 75-138 OTHERREFERENCES A. J. Field et al., The Electrical Conductivity of Alumi numWire, Journal of the Institute of Metals, 1933, 51, 183-198.

H. J. Miller, Heat-Treatment and Finishing Operations in the Productionof Copper and Aluminum Rod and Wire, Journal of the Institute of Metals,1954-55, 83, 221-232.

Alloy Digest, Aluminum EC, filing code, AL-104, June 1961, 2 pages,published by Engineering Alloys Digest, Inc., Upper Montclair, NJ.

Horn et al., Aluminum-Conductor Cable an Alternative to Copper, BellLaboratories Record, November 1967, pp. 314-319.

Transactions of the American Society for Metals, The Eifect of SingleAddition Metals on the Recrystallization, Electrical Conductivity andRupture Strength of Pure Aluminum, 1949, vol. 41, pp. 443 to 459.

Ya. M. Krupotkin et al., Effect of Small Impurities of Iron, Nickel, andCobalt on the Mechanical Properties and Electrical Conductivity ofAluminum, Izv. Vysshikh Uchebn. Zavedenii, Energ. 8, No. 10, 112-116,1965.

Gaston G. Gauthier, The Conductivity of Super-Purity Aluminum: TheInfluence of Small Metallic Additions, Journal of the Institute ofMetals, 1936, 59, 129-150.

RICHARD O. DEAN, Primary Examiner US. Cl. X.R.

